Temperature-staged cryogenic apparatus

ABSTRACT

A cryogenic apparatus in which fluid is circulated between fluid chambers through a fluid flow path including two or more regenerators, the coldest regenerator being positioned in a tubing affixed to the cold end and around which a portion of the displacer moves to define a low-temperature refrigeration chamber. An intermediate-temperature refrigeration chamber is defined within the displacer, thus forming a two-staged device with a single displacer. The arrangement is suitable for multistage apparatus and is applicable to several different cycles.

[451 Mar. 21, 1972 [54] TEMPERATURE-STAGED CRYOGENIC APPARATUS [72] Inventor: James A. O'Neil, Bedford, Mass.

[73] Assignee: Cryogenic Technology. Inc., Waltham,

Mass.

22 Filed: Oct. 20, 1969 21 Appl.No.: 867,661

3,292,501 12/1966 Verbeek ..62/6

Schulze ..62/6

Primary Examiner-William J. Wye Attorney-Bessie A. Lepper 5 7] ABSTRACT A cryogenic apparatus in which fluid is circulated between. fluid chambers through a fluid flow path including two or more regenerators, the coldest regenerator being positioned in a tubing amxed to the cold end and around a ortion of [51] f" Cl F251, 9/00 the displacer moves to define a low-temperature refrigeration [58] Fleld 01 Search ..62/6 chamber. An intermediae4emperature refrigeration chamber is defined within the displacer, thus forming a two-staged [56] References cued device with a single displacer. The arrangement is suitable for UNITED STATES PATENTS multistage apparatus and is applicable to several different cycles. 3,221,509 12/1965 Garwin ..62/6 I 3,248,870 5/1966 Morgenroth ..62/6 24 Claims, 9 Drawing Figures P HP L 49 X kw PATENTEDHARZ] I972 3,650,118

sum 1 UF 5 INVENTOR. James A. O'Neil AHorney PATENTEDMARZ] I972 3,6501 18 sum 3 OF 5 INVENTOR. James A. O'Neil Aiforney PATENTEUHARZ'I 1912 SHEET Q [1F 5 ISI I62 I55 I63 I56 I52 Ono O OH) INVENTOR. James A O'Neil Ar'rorney PATENTEDMAR 21 I972 SHEET 5 BF 5 Fig, 9

INVEN'RJR. James A. O'Neil TEMPERATURE-STAGED CRYOGENIC APPARATUS This invention relates to cryogenic equipment and, more particularly, to cryogenic refrigerators which are capable of delivering refrigeration in a temperature range of from about 150 to 15 K. with very rapid cooldown.

U.S. Pat. Nos. 2,906,101 and 2,966,035 describe a refrigerator cycle in which high-pressure fluid is introduced into a refrigeration chamber through a flow path including a regenerator to build up a predetermined quantity of initially cooled high-pressure fluid in a refrigerator chamber. Then, after cutting off the supply of high-pressure fluid, the initially cooled high-pressure fluid is expanded further to cool it and deliver refrigeration to an externally-linked load. Both of these patents also disclose staging of the cycle in order to obtain refrigeration at lower temperatures than are possible with sin gle-stage refrigerators. In some of the prior art devices such staging is achieved by providing a series of successively colder chambers in parallel with each other using separate cylindrical housings and separate displacers joined to a common head block (see, for example, FIG. 7 of U.S. Pat. No. 2,966,035). Alternatively, the succeeding colder chambers are located within a single housing of a stepped configuration, a construction which requires the joining of a series of cylindrical sections of decreasing diameter (see, for example, FIG. 6 of U.S. Pat. No. 3,218,815). In a somewhat similar manner it has also been customary to stage Stirling and Vuilleumier refrigerators.

In many applications of these types of apparatus it is not necessary to achieve rapid cooldown of the stages, and in many applications there are no reasons for desiring any great degree of flexibility in construction procedures or in displacement ratios. However, in some instances it would be desirable to have a cryogenic refrigerator which could be constructed with the ease and at essentially the same cost as the singlestage refrigerator but which, at the same time, could be used to obtain the lower temperatures associated with two-stage devices. Further, it would be desirable to have such a refrigerator which could be designed to be cooled down at a rapid rate and which would be readily adaptable to optimization in performance with respect to displacement ratios and the like.

It is therefore a primary object of this invention to provide a cryogenic apparatus which is capable of delivering refrigeration in a cryogenic range, and which exhibits the combination of low-temperature refrigeration and rapid cooldown. It is another object of this invention to provide a cryogenic refrigerator of the character described which is built essentially as a single-stage device but has, in effect, two stages with a single displacer, thus simplifying construction and reducing cost for a given temperature or refrigeration capacity, while providing a stiffer cylinder assembly. It is another object of this invention to provide a cryogenic refrigerator of the character described which may be designed to have a larger cold tip displacement than can be generally obtained with a stepped two-stage refrigerator and hence to provide more rapid cooldown of the cold tip mass.

it is another object of this invention to provide such an apparatus which is adaptable to any size refrigerator, which can be formed to operate on the work, no-work, Stirling or Vuilleumier cycle, and which can be combined with additional stages, the latter combination being suitable for integration with a Joule-Thomson loop to provide an apparatus capable of liquefying at least some of the cryogenic gases. Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which FIG. 1 is a longitudinal cross section of a two-stage refrigerator designed to operate on the no-work cycle of U.S. Pat. No. 2,966,035 and constructed in accordance with this invention;

FIG. 2 is a cross section of the refrigerator of FIG. 1 taken along line 2-2 of FIG. 1;

FIG. 3 is a modification of the apparatus of FIG. 1 showing the use of a pneumatic driving system and the auxiliary components completing the apparatus;

FIG. 4 is a longitudinal cross section of a refrigerator constructed in accordance with this invention and designed to operate on the work cycle described in U.S. Pat. No. 2,906,101;

FIG. 5 is a longitudinal cross section of a three-stage refrigerator incorporating an additional intermediate temperature stage in a modified stepped refrigerator;

FIG. 6 is a diagrammatic representation of the refrigerator of FIG. 5 integrated with a Joule-Thomson loop in order to provide an apparatus capable of liquefying cryogenic gases;

FIG. 7 is a somewhat diagrammatic, longitudinal cross section of a refrigerator constructed in accordance with this invention and designed to operate on the so-called Vuilleumier cycle described in U.S. Pat. No. 1,275,507;

FIG. 8 is a somewhat diagrammatic, longitudinal cross section of a refrigerator constructed in accordance with this invention and designed to operate on the Stirling cycle; and

FIG. 9 is a cross section of a modification of a three-staged device in which the housing and displacer have the same diameter throughout.

The refrigerator of this invention is of the class which delivers refrigeration through a cold-end heat station and which comprises a housing having a displacer movable therein to define a first low-temperature and a second intermediatetemperature fluid chamber of variable volumes, means to move the displacer, and a fluid flow path providing fluid communication between the chambers, the flow path incorporating first and second regenerators, the second regenerator being located within the displacer. Compression of the fluid after expansion may be done externally of the housing and the compressed fluid introduced through valve-controlled conduits as in the case of the work and no-work cycles; or compression may be accomplished in a separate chamber (using a second movable body) which is in fluid communication with one or more expansion chambers through a fluid flow path which contains no valves such as in the Vuilleumier or Stirling cycles.

The refrigerator of this invention is characterized in that the first heat storage means associated with the low-temperature refrigeration chamber is located within a fixed cylindrical tubing extending from the heat station through a portion of the length of the housing and generally coaxial therewith. This cylindrical tubing defines with the internal wall of the housing a volume within the housing which in the preferred embodiments is of an annular configuration. The displacer is formed to have an annular section movable within this annular volume to define the cold, low-temperature refrigeration chamber in the form of an annulus of variable volume. The second, or intermediate-temperature, refrigeration chamber is located within the annular section of the displacer. Thus, a single displacer in its motion defines two refrigeration chambers of variable volume, and a multistage device may be constructed within a cylindrical housing which need not be of a stepped configuration or of a configuration requiring two displacers depending from a single head block and moving within separate parallel cylindrical housings.

The apparatus illustrated in cross sectional detail in FIGS. 1 and 2 is adapted to operate on the so-called no-work cycle described in U.S. Pat. No. 2,966,035. The apparatus of these figures has a single displacer and two refrigeration chambers, and is designed to deliver refrigeration to an external load at a temperature from about to 15 K. It will be seen that there is provided a housing 10 having an upper flange 11 adapted for attachment to a crosshead 12 through sealing means 13. The housing is sealed on the lower end by means of a thermal connecting plate 14 typically constructed of copper, or a material having a high heat conductivity at cryogenic temperatures, and forming a part of the heat station to be described in detail below. Inasmuch as the crosshead is not part of the invention, it is not shown in detail; however, it may take any suitable form such as, for example, that described and claimed in US. Pat. No. 3,312,239.

For convenience, in the following description terms such as upper" and lower may be used, but in the case of terms used to describe the various temperatures of the volumes cold," "intermediate-temperature and warm), these terms are relative. It will, of course, be appreciated that the refrigeration apparatus may be oriented in any fashion desired and hence the terms upper" and lower are merely used in connection with the apparatus orientation illustrated in the figures.

Within housing a displacer, generally indicated by the reference numeral 17, defines the various chambers, and in the apparatus of this invention the displacer is formed of an upper or what may be termed a cylindrical section 18 and a lower or annular section 19. Since the annular portion of the displacer is to be used to define chambers within the housing, it is necessary to provide some means of sealing off the chambers as well as some means to guide the annular section of the displacer. This is done through the incorporation of a tubing 24 which is mounted to the cold end in the thermal connecting piece 14 and, therefore, is attached to the heat station. This tubing'24 extends partly through the length of the housing 10, its dimensions (length and diameter) being determined by the dimensions of the intermediate-temperature chamber desired. Tubing 24 is preferably formed of a material, such as stainless steel, which has good strength and a relatively low thermal conductivity at cryogenic temperatures. If desired, a sealing ring 25 may be located with the internal walls of the annular section 19 of the displacer in order to insure a fluidtight seal with the outer wall of tubing 24. Alternatively, the sealing ring may be positioned in the tubing wall. An annular ring 26 formed of a material such as copper is positioned at the bottom of the annulus formed between the housing and the tubing 24. Ring 26 and thermal connecting piece 14 may be a single integral member. Between this heat station ring and the annular displacer section 19 is defined the first or low-temperature refrigeration chamber 27. Ring 26 has plurality of passages 28 in it; and these passages are aligned with passages 29 in the tubing. This becomes part of the fluid flow path connecting the low-temperature refrigeration chamber 27, in the form of an annulus, and the first regenerator 30 which is located within the tubing 24. In the embodiment shown in FIG. 1, this regenerator is formed of a bottom stack of screens 31, a felt pad 32, and a filling of lead balls 33 extending throughout substantially the length of the tubing 24. At the top end of the regenerator 30, the arrangement is similar to that at the bottom end and includes a felt pad 34 and a series of screens 35. Any suitable regenerator packing with appropriate retaining means may be used.

The intermediate-temperature refrigeration chamber will be seen to be located within the annular section 19 of the displacer and defined between the top of the regenerator 30 and the bottom of the regenerator 42 which is located within the cylindrical section 18 of the displacer. It will be seen that as the displacer moves up and down the volume of the intermediate-temperature chamber 40 is varied. As illustrated in FIG. 1, the second regenerator has a perforated plate 43 positioned at its bottom end to retain within the regenerator a series of stacked screens 44. It will, of course, be appreciated that the regenerators 30 and 42 may be made of any wellknown regenerator materials, these being only illustrative of two types of regenerators which are usable.

A series of fluid passages 45 connect the upper regenerator 42 with a third or warm chamber 46. This chamber, in turn, is connected to a source of high-pressure fluid as well as to a low-pressure reservoir through an external conduit 47. A rod 48 is attached to the upper end of the displacer to link it mechanically to a suitable driving means.

- It is also, of course, within the scope of this invention to operate the displacer through pneumatic driving means, i.e., a driving chamber positioned in driving relationship to the displacer within the refrigerator. Such a pneumatic driving means is shown somewhat diagrammatically in FIG. 3 in which like numbers refer to like components of FIGS. 1 and 2. Atfixed to housing 10 is a housing extension 49 and attached to the upper portion of the displacer 17 is a piston 50 which reciprocates within a housing extension 49 to define a driving volume 51 of variable volume. High-pressure fluid is introduced into the driving chamber 51 and withdrawn from the chamber through a fluid conduit 52. In the modification shown in FIG. 3, the driving fluid used in chamber 51 is the same as the refrigeration fluid circulating within the refrigerator. Thus, there is provided a single high-pressure fluid source 53 along with a high-pressure fluid line 54 and its associated valve 55, the high-pressure line 54 being in fluid communication with the external conduit 47. There is also provided a lowpressure reservoir 56, a low-pressure line 57 and valve 58 which are also in communication with the external conduit 47. In like manner, high-pressure line 59 controlled by valve 60 connects the high-pressure fluid source 53 with the conduit 52, and a low-pressure line 61 controlled by valve 62 forms the necessary fluid communication between conduit 52 and the low-pressure reservoir 56. Finally, there is provided a connecting means 63 between the low-pressure and high-pressure sides of the system, this connecting means having associated with it a compressor 64 and an aftercooler and cleanup systems 65. The operation of the valves and of the fluid driving system is essentially that which is described in US. Pat. No. 3,188,819 and need not be described further in this disclosure.

It is also possible to provide separate high-pressure sources and low-pressure reservoirs for the driving chamber 51 and for the refrigerator. Separate compressors and aftercoolers are then required. Alternatively, the systems of FIGS. 1 and 3 may be used in open cycles, in which cases compressed fluids would be supplied from an external source and the low-pressure fluid discharged to the surroundings.

Inasmuch as the refrigerators of FIGS. 1, 2 and 3 operate on a well-known cycle, it is not necessary to describe this cycle in detail. Rather, the fluid flow path within the refrigerator may be briefly traced in order to understand the manner in which the refrigeration is developed. To begin with, high-pressure fluid isintroduced through the external conduit 47 into the warm chamber 46 from where, with the movement of the displacer upwardly, it passes down through fluid passages 45, regenerator 42 and into intermediate temperature chamber 40. A portion of it is also caused to flow downwardly through the regenerator 30 and out through the heat station by way of radial passages 29, fluid passages 28 and into the low-temperature refrigeration chamber 27. By providing the passageway system through the heat station the maximum amount of refrigeration can be delivered from a moving stream to a load thermally linked to the connecting member 14. In this apparatusno refrigeration is delivered from the intermediatetemperature refrigeration chamber 40 because the heat transfer path is through the moving displacer and it is typically formed of a low thermal conductivity material such as Micarta. However, by constructing a portion of the annular section of the displacer of a material having good low-temperature thermal conductivity, it is possible to associate a heat station with the intermediate-temperature chamber. This modification is illustrated in the apparatus of FIG. 4 and is applicable to the apparatus embodiments of FIGS. 1 and 3.

After the high-pressure fluid supply has been cut off, it is then necessary to move the displacer upwardly, the distance being dependent upon the cycle modification which may be used. Thus, the displacer may be moved all the way up or only a part of the way up before the low-pressure valve is opened and the high-pressure initially cooled fluid allowed to exhaust to the low-pressure reservoir.

displacers. This design also eliminates any universal pin joint between displacers such as may be required in the apparatus shown in US. Pat. No. 3,218,815. The apparatus of this invention also lends itself very readily to adjustments in performance inasmuch as the displacement ratios of the displacer and hence the volume ratios of chambers 27 and 40 may be readily altered by changing the dimensions of the apparatus.

The apparatus of FIG. 4 which is constructed in accordance with the teaching of this invention is adapted to operate on the so-called work cycle described in detail in US. Pat. No. 2,906,10l. In this drawing like reference numerals are used to identify like components shown in FIGS. 1-3. The apparatus of FIG. 4 differs from that of FIG. 1 in that the housing is open at the top and no third or warm chamber is provided. This requires that seals must be used at the warm end of the apparatus, and therefore the housing is preferably somewhat modified to strengthen the upper section. Therefore, the housing is shown to comprise a lower housing section 68 and an upper housing section 69, the latter being opened at the top 70, as indicated. The displacer, generally indicated by the reference numeral 67, of this embodiment is constructed in three sections, namely a lower or annular section 71 formed of a low thermal conductivity material, an intermediate section 72, of a length which approximates the maximum height of the intermediate-temperature chamber 40, formed of copper or some other suitable high thermal conductivity material, and an upper cylindrical section 73 which contains regenerator 42 and which is equipped with an upper sealing ring 74 and a lower sealing ring 75. In this arrangement, it is, of course, necessary to provide some modified system for introducing the high-pressure fluid into and withdrawing the low-pressure fluid from the upper or warmer regenerator 42. This is done by modifying the upper or solid section 72 of the displacer to provide an annular passage 76 defined between the outer displacer wall and the inner wall of the upper housing 69. This annular passage is then connected for fluid communication with the regenerator 42 through a plurality of radial passages 77 drilled in the displacer. The annular passage 76 must, of course, be of such a length that it is always open to the external conduit 47 throughout the full stroke of the displacer. In the refrigerator of FIG. 4 the bottom regenerator 30 is shown to be filled with a metallic wool 78 illustrating a modification in the regenerator filling which is possible in the construction of this apparatus.

When the displacer is constructed as shown in FIG. 4 to have an intermediate annular section 72 formed of a material having high thermal conductivity it is possible to derive refrigeration from the fluid in the intermediate-temperature chamber 40. This may be done by bonding coils 79 to housing section 68, the coils being suitable for circulating a heat transfer fluid therethrough.

An examination of FIG. 4 will show that the fluid flow path in this apparatus is by way of conduit 47, annular passage 76, radial passage 77, regenerator 42, intermediate-temperature refrigeration chamber 40, regenerator 30, passages 28 and 29 in the heat station and finally the low-temperature refrigeration chamber 27. The discharge of the fluid from the regenerator is, ofcourse, in the opposite direction.

Although the apparatus of this invention is designed to simplify and reduce the cost of construction of a two-stage singledisplacer type refrigeration chamber and to provide a stiffer cylinder assembly, the basic concept is also applicable to a three-stage refrigerator in which one of the stages may be provided as a stepped configuration or as a separate housing and displacer. An arrangement using a stepped configuration is illustrated in FIG. 5 in which the two lower-temperature refrigeration chambers 27 and 40 are provided in the same configuration as in FIG. 1 and in which like numbers refer to like components.

In order to provide the stepped configuration and the additional intermediate-temperature refrigeration volume, the housing is constructed of a lower or smaller-diameter section 80 corresponding to housing of FIG. 1 and of an upper or larger-diameter section 81, these being joined by a ring 82. In like manner, the displacer, generally indicated by the reference numeral 83, comprises an upper section and a lower section, indicated by the reference numeral 84, formed of a cylindrical portion 86 and an annular portion 87. Sealing rings 90 and 92 are provided to isolate the various chambers within the refrigerator. The warm chamber 94 is now defined within the upper larger section of the refrigerator and there is also provided an additional intermediate-temperature refrigeration chamber 95. A third regenerator formed of stacked screens 101 is positioned within the displacer section 85. One or more fluid passages 102 provide fluid communication between the warm chamber 94 and regenerator 100, and likewise a central fluid passage 105 provides communication between the regenerator 100 and the lower regenerator 42. In addition, a plurality of radial passages 106 connect the intermediate-temperature refrigeration chamber 95 with the regenerator 100. The apparatus of FIG. 5 is also shown to have two coils 110 and 111 suitable for circulating a heat transfer fluid and for extracting refrigeration from the apparatus of FIG. 5. The central section of the annular portion 87 of the displacer may be modified as in FIG. 4, in which case an additional coil would be added corresponding to coil 79 of FIG. 4.

FIG. 6 illustrates the integration of a Joule-Thomson loop 113 with the refrigerator 112 of FIG. 5. Therefrigerator of FIG. 5 is sketched in in FIG. 6 and like numbers refer to like elements in that drawing. FIG. 6 illustrates the connection of the rod 48 to some suitable driving means, such as a crank 114, as well as connection of fluid conduit 47 to a high-pressure fluid source and a low-pressure fluid reservoir. High-pressure fluid is supplied from a high-pressure fluid source 115 and taken by line 116, controlled by valve 117, into the refrigerator fluid conduit 47 as well as into the Joule-Thomson loop. In like manner low-pressure fluid is returned to the lowpressure reservoir through line 121 controlled by valve 122. If desired, the high-pressure source and the low-pressure reservoir may be connected as through conduit 125 which has associated with it a compressor 126 and an aftercooler and optional cleanup system 127 The high-pressure line 130 of the Joule-Thomson loop is connected to the high-pressure fluid source 115 and passes through a first Joule-Thomson loop heat exchanger 131, a first heat station heat exchanger 132 which is in thermal contact for indirect heat exchange with the fluid in refrigeration chamber 95 of the refrigerator, a second Joule-Thomson loop heat exchanger 133, a second heat station heat exchanger 134 for indirect heat exchange with the fluid in chamber 40, a third Joule-Thomson loop heat exchanger 135, and a third heat station heat exchanger 136 which is designed for thermal connection for indirect heat exchange with the fluid in the low-temperature refrigeration chamber 27 of the refrigerator. Finally, the initially cooled high-pressure fluid in the Joule- Thomson loop is taken through a Joule-Thomson heat exchanger 137 and through a Joule-Thomson expansion valve 138 where the cold (and possibly liquefied) fluid is discharged into a reservoir 139. At least a portion of the cold, low-pressure fluid in reservoir 139 is then returned through the lowpressure line 140 which passes up through the Joule-Thomson loop heat exchangers 137, 135, 133 and 131 to be taken into the low-pressure reservoir 120, for compressing and returning into the system, by way of line 140.

As previously noted, this invention is also applicable to cryogenic refrigerators which contain compressor means in a direct flow path with the expanders without using valves. Two such refrigerators are illustrated in FIGS. 7 and 8. The apparatus of FIG. 7 operates on the basic cycle described in US. Pat. No. 1,275,507 as well as the particular cycle described in the Proceedings of the 1956 Cryogenic Engineering Conference, University of Colorado, Boulder, Colorado (February 1957), pp. 188-196. This cycle may, for convenience, be referred to as the Vuilleumier cycle.

be constructed and used in accordance with known art.) Theinternal volume defined by housing 151 is divided into four chambers of variable volume, conveniently designated as the warm chamber 152, the intermediate-temperature chamber 153 and two cold or expansion chambers 154 and 155, chamber 154 having the coldest fluid which is used to deliver refrigeration to a load. The chambers are defined within the housing and their volume controlled through the movement of two displacers. The first of these is displacer 156 which contains a regenerator 157 having forarninous (or other suitable) port plates 158 and 159 and which is driven through rod 160 by any suitable mechanical or pneumatic means. The second displacer 161 is formed, according to the teaching of this invention, of a cylindrical section 162 and an annular ring section 163. A regenerator 164, contained between forarninous port plates 165 and 166, is located in the solid section 162, while the internal wall of the annular section 163 makes a sliding seal with the external wall of tubing 170. A regenerator 171 is located in tubing 170 closed over by screening 173. The regenerator 171 is so designed as to permit rod 167, which is attached to displacer 161 for driving, to reciprocate throughout the length of this regenerator. A plurality of ports 172 provide fluid communication between chamber 154 and regenerator 171.

Suitable heat exchange means are associated with the chambers-e.g., coils 175 with chamber 152, coils 176 with chamber 153 and coils 177 with chamber 154. In keeping with the cycle for which the apparatus is designed the displacers 156 and 161 will be moved to vary the volumes of chambers 152, 153 and the combination of chambers 154 and 155. Heat to achieve compression is put into the system through heat transfer with fluid flowing in coils 175, heat is rejected through heat transfer with fluid flowing in coils 176, and refrigeration is delivered through heat transfer to fluid circulated in coils 177. For cryogenic applications a typical temperature sequence would be ambient temperature for fluid in coils 175, liquid nitrogen temperature for fluid in coils 176 and between about and K. for fluid in coils 177.

In the operation of the apparatus of FIG. 7 the volume of the fluid system remains constant while the fluid is shuttled among the chambers through the regenerators. The two displacers are phase-separated by about 90 and the sequence of displacer motion may be briefly described as follows, beginning with the displacers occupying their outermost positions as shown in the apparatus orientation of FIG. 7. Displacer 156 is moved inwardly to transfer fluid into compression chamber 152' from chamber 153 while displacer 161 remains in its outermost position. Then displacer 163 is moved inwardly transferring fluid from chamber 153 to chambers 155 and 154 and cooling it through heat transfer and expansion while displacer 156 occupies its innermost position. At the end of this step, the volume of chamber 153 is essentially zero while the volumes of chambers 152, 155 and 154 are maximum. Then displacer 156 is moved outwardly to compress the fluid in chamber 152 and transfer it back into chamber 153. Finally, displacer 163 moves outwardly to transfer cold liquid through regenerators 171 and 164 to store refrigeration for the next cycle.

A two-staged Stirling cycle engine is illustrated in FIG. 8. This apparatus operates on a closed system wherein compression is achieved mechanically in contrast to its achievement by the addition of heat as illustrated in the apparatus of FIG. 7. This closed system is contained within an enclosure generally indicated by the numeral 180 which consists of a bottom section 181 housing the drive mechanism, and a main section 182 housing the compressor and the expansion chambers. A compressor piston 183 with suitable sealing rings 184 is driven through rods 185 from drive shaft 186 by motor 187. In the main housing 182 there is a displacer 188 which, according to this invention, has a cylindrical section 189 and an annular section 190. The displacer 188 is driven off shaft 186 through rod 191. In their movement within the enclosure, piston 183, and displacer 188 define a compressor chamber 195, a first expansion chamber 196, and a second expansion chamber 197. The displacer 188 has a regenerator 198 located in its.

cylindrical section and terminating in a forarninous port plate 199. The fluid path between this regenerator and compression chamber 195 comprises an annular passage 200 and a plurality of radial passages 201. The annular section 190 of the displacer makes a sliding seal with the tubing 202 to define the refrigeration chambers 196 and 197. Regenerator 203, terminating in a screen 204, is located in tubing 202 which has a plurality of fluid ports 205 to provide fluid communication between chamber 196 and regenerator 203. A heat station 206 is associated with the first or coldest chamber 196 and it is adapted to deliver refrigeration to a load. A heat station 207 is associated with the compressor chamber and it is adapted through fluid circulating in coils 208 for cooling the compressed fluid prior to its delivery to regenerator 198.

The cycle on which the refrigerator of FIG. 8 operates is not a part of this invention but it may be described briefly as follows. With the displacers in the up position the piston 183 is moved up causing compression of the gas in chamber 195. As the displacer 188 is moved downwardly to displace high-pressure gas from chamber 195 into low-temperature chambers 197 and 196 the piston continues to move upwardly to maintain high pressure. When the chambers 197 and 196 are at maximum volume by the downward movement of displacer 188 the piston 183 is moved downwardly causing expansion of the gas in chambers 196 and 197. On full expansion of the gas the displacer 188 is moved upwardly to displace the expanded and cooled gas out of volumes 196 and 197, while the piston 183 continues to move downwardly to maintain low pressure. The idealized cycle described is in practice modified by the fact that the displacer and piston have a simple sinusoidal motion with a phase separation of about 90 in their motions which closely approximates the cycle described. As the gas is displaced from chamber 195 through regenerators 198 and 203 it is cooled. The heat of compression is removed by passage of the gas on displacement from chamber 195 through annular heat exchange path 200 to heat station 207 and cooling fluid in coils 208.

Each of the refrigerators of FIGS. 7 and 8 may, of course, be further staged in the same manner as illustrated in FIG. 5 and each may be integrated with a Joule-Thomson loop in a manner similar to that shown in FIG. 6.

FIG. 9 shows an alternate multistaged device wherein the internal configuration of the displacer and the tubing with which it makes a sliding seal are stepped. Although this configuration is suitable for delivering refrigeration at the coldest level (typically at about 20 K.) it is not designed to deliver refrigeration efficiently from the intermediate expansion chamber or to deliver any refrigeration from the highest temperature level expansion chamber. It will be apparent to anyone skilled in the art that the staging arrangement shown in FIG. 9 for no-work cycle apparatus (FIG. 1) is equally adaptable for work cycle apparatus (FIG. 4), for Vuilleumier cycle apparatus (FIG. 7), and for Stirling cycle apparatus (FIG. 8).

The housing 215 and displacer 216 of the apparatus of FIG. 9 are cylindrical. The housing has a top cover 217 and a heat station 218 on the cold end. (For simplicity of presentation, no seals are shown since these are within the skill of the art.) The displacer 216 is internally configured to efiectively divide it into three sections-namely, the upper cylindrical section 219, the middle annular section 220 and the lower annular section 221. In like manner, the centrally positioned tubing or regenerator housing 222 has an upper section 223 and a lower, larger-diameter section 224. The displacer, in its motion, defines four fluid chambers of variable volumes, i.e., chambers 225, 226, 227 and 228. A regenerator 229 and fluid ports 230 and 231 provide fluid communication between chambers 225 and 226; while regenerators 232 and 233 and fluid ports 234, 235, 236 and 237 provide fluid communication among the expansion chambers 226,227, and 228.

By providing the cold end regenerator in the fixed guide tubing, forming the displacer in the manner described and using the flow path through a cold end heat station, it is possible to form a cryogenic refrigerator in the configuration of a single-stage device while providing the lower-temperature refrigeration and the efficiency associated with a two-stage apparatus. Moreover, the cold end will cool a mass more rapidly than a prior art type staged refrigerator because of the larger practical displacement achieved. Moreover, a single cylinder is a stiffer configuration than a two-staged, stepped multicylinder configuration and is more simple and less expensive to construct. Finally, with the regenerator attached to the cold tip it is possible to use more efficient heat stations, such, for example, as those described in copending application Ser. No. 807,606 filed Mar. 17, 1969, in the names of Fred F. Chellis and James A. ONeil and assigned to the same assignee as the present application.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

lclaim:

l. A cryogenic apparatus adapted to deliver refrigeration to an external load through a heat station, comprising a fluidtight housing having a displacer movable therein to define a first fluid chamber of variable volume and a second fluid chamber of variable volume, means to move said displacer, and a fluid flow path providing fluid communication between said chambers, said flow path incorporating first and second heat storage means, said second heat storage means being located within said displacer, characterized in that said first heat storage means is located within a fixed regenerator housing extending from said heat station through a portion of the length of said fluidtight housing, said regenerator housing defining a cavity to with the internal wall of said fluidtight housing, that a portion of said displacer is configured to be movable within said cavity to define said first chamber and that said second chamber is defined within said displacer.

2. A cryogenic apparatus adapted to deliver refrigeration to an external load through a heat station, comprising a fluidtight housing having a displacer movable therein to define a first fluid chamber of variable volume and a second fluid chamber of variable volume, means to move said displacer, and a fluid flow path providing fluid communication between said chambers, said flow path incorporating first and second heat storage means, said second heat storage means being located within said displacer, characterized in that said first heat storage means is located within a fixed regenerator housing extending from said heat station through a portion of that length of said fluidtight housing and coaxial therewith to define an annular cavity within said housing, that said displacer is formed to have an annular section movable within said annular cavity to define said first chamber in the form of an annulus and that said second chamber is defined within said annular section ofsaid displacer.

3. A cryogenic apparatus, comprising in combination a. a housing terminating at its cold end in means adapted to deliver refrigeration;

b. a cylindrical tubing internal of and coaxial with said housing, extending from said cold end through a portion of the length of said housing and defining an annular spacing with the internal wall of said housing;

c. a first regenerator within said cylindrical tubing;

d. a displacer movable within said housing and comprising a cylindrical portion and an extended annular portion, said annular portion being adapted to move within said annular spacing;

e. a second regenerator located within said cylindrical portion of said displacer;

f. a first refrigeration chamber within said annular spacing having a volume variable with the movement of said displacer and in fluid communication with said first regenerator;

g. a second refrigeration chamber defined within said annular portion of said displacer, having a volume variable with the movement of said displacer and in fluid communication with said first and second regenerators;

h. fluid flow path means including said regenerators and refrigeration chambers and adapted to permit fluid circulation through said apparatus; and

i. means to impart motion to said displacer.

4. An apparatus in accordance with claim 3 including a third chamber of variable volume, said third chamber being in fluid communication with said second regenerator.

5. An apparatus in accordance with claim 4 wherein said third chamber is within said housing and said apparatus includes a piston operating in conjunction with said displacer to vary the volume of said third chamber.

6. An apparatus in accordance with claim 3 including a second displacer having heat storage means therein and being independently operable to define third and fourth chambers of variable volume, said third and fourth chambers having heat transfer means associated therewith.

7. An apparatus in accordance with claim 3 wherein said housing and said cylindrical portion of said displacer are of a stepped configuration, thus having two sections of different diameter and defining a third refrigeration chamber of variable volume, and wherein the larger-diameter section of said displacer contains a third regenerator in fluid communication with said third refrigeration chamber and said third regenerator is part of said fluid flow path means.

8. An apparatus in accordance with claim 7 including a fourth chamber of variable volume, said fourth chamber being in fluid communication with said third regenerator.

9. An apparatus in accordance with claim 3 wherein said cylindrical tubing and the internal configuration of said annular portion of said displacer are stepped, thereby defining a third refrigeration chamber of variable volume within said displacer, and wherein said tubing contains a third regenerator in fluid communication with said second and third refrigeration chambers and said first regenerator.

10. An apparatus in accordance with claim 3 wherein said means to impart motion to said displacer comprises a rod and means to drive said rod whereby said displacer is driven mechanically.

11. An apparatus in accordance with claim 3 wherein said means to impart motion to said displacer comprises a piston affixed to said displacer, a fluid chamber associated with said piston, and means to introduce into and withdraw a fluid from said fluid chamber whereby said displacer is driven pneumatically.

12. An apparatus in accordance with claim 3 wherein that part of said annular portion of said displacer which defines said second refrigeration chamber is formed of a material exhibiting high heat conductivity whereby heat may be exchanged between the fluid in said second refrigeration chamber and an external load.

13. An apparatus in accordance with claim 3 including highpressure fluid supply means, a low-pressure fluid reservoir, and valve-controlled fluid conduit means providing fluid communication between said fluid supply means and said fluid reservoir and said second regenerator.

14. An apparatus in accordance with claim 13 wherein said high-pressure fluid supply means and said low-pressure fluid reservoir are combined in the form of a fluid compressor.

15. An apparatus in accordance with claim 13 including a third chamber of variable volume positioned in said fluid flow path between said valve-controlled fluid conduit means and said second regenerator.

16. A cryogenic apparatus adapted to deliver refrigeration to an external load at a plurality of temperature levels, comprising in combination a. a housing formed in a stepped configuration and having two coaxial sections of different diameters, the end of the smaller-diameter section being the cold end and being adapted to deliver refrigeration at the lowest temperature; b. a cylindrical tubing internal of said smaller-diameter secchamber and adapted to effect heat exchange between fluid in said chambers and an external load; and

1. means to impart motion to said displacer.

17. An apparatus in accordance with claim 16 wherein heat tion, extending from said cold end through a portion of 5 station means are associated with said second refrigeration the length of said smaller-diameter section and defining an annular spacing with the internal wall thereof;

c. a first regenerator within said cylindrical tubing;

d. a displacer of stepped configuration formed of two sections of different diameters, the larger-diameter section being movable in the larger-diameter housing section and the smaller-diameter section being movable in the smaller-diameter housing section, the smaller-diameter section having a cylindrical portion and an extended annular portion, said annular portion being adapted to move within said annular spacing;

e. a second regenerator located within said cylindrical portion of said smaller-diameter section of said displacer;

f. a third regenerator located within said larger-diameter section of said displacer;

g. a first refrigeration chamber within said annular spacing having a volume variable with the movement of said displacer and in fluid communication with said first regenerator;

h. a second refrigeration chamber defined within said annular portion of said displacer, having a volume variable with the movement of said displacer and in fluid communication with said first and second regenerators;

i. a third refrigeration chamber defined in said larger-diameter housing section, having a volume variable with the movement of said displacer and in fluid communication with said second and third regenerators;

j. fluid flow path means including said regenerators and refrigeration chambers and adapted to permit fluid circulation through said apparatus;

k. heat station means associated with at least said first refrigeration chamber and said third refrigeration chamber and wherein that part of said annular portion of said displacer which defines said second refrigeration chamber is formed of a material exhibiting high heat conductivity whereby heat may be exchanged between the fluid in saidsecond refrigeration chamber and said heat station means associated therewith.

18. An apparatus in accordance with claim 16 wherein said external load comprises a Joule-Thomson loop.

19. An apparatus in accordance with claim 16 including a fourth chamber of variable volume, said fourth chamber being in fluid communication with said third regenerator.

20. An apparatus in accordance with claim 19 wherein said fourth chamber is within said housing and said apparatus includes a piston operating in conjunction with said displacer to vary the volume of said fourth chamber.

21. An apparatus in accordance with claim 16 including a second displacer having heat storage means therein and being independently operable to define fourth and fifth chambers of variable volume, said fourth and fifth chambers having heat transfer means associated therewith.

22. An apparatus in accordance with claim 16 including high-pressure fluid supply means, a low-pressure fluid reservoir, and valve-controlled fluid conduit means providing fluid communication between said fluid supply means and said fluid reservoir and said second regenerator.

23. An apparatus in accordance with claim 22 wherein said high-pressure fluid supply means and said low-pressure fluid reservoir are combined in the form of a fluid compressor.

24. An apparatus in accordance with claim 22 including a fourth chamber of variable volume positioned in said fluid flow path between said valve-controlled fluid conduit means and said second regenerator. 

1. A cryogenic apparatus adapted to deliver refrigeration to an external load through a heat station, comprising a fluidtight housing having a displacer movable therein to define a first fluid chamber of variable volume and a second fluid chamber of variable volume, means to move said displacer, and a fluid flow path providing fluid communication between said chambers, said flow path incorporating first and second heat storage means, said second heat storage means being located within said displacer, characterized in that said first heat storage means is located within a fixed regenerator housing extending from said heat station through a portion of the length of said fluidtight housing, said regenerator housing defining a cavity to with the internal wall of said fluidtight housing, that a portion of said displacer is configured to be movable within said cavity to define said first chamber and that said second chamber is defined within said displacer.
 2. A cryogenic apparatus adapted to deliver refrigeration to an external load through a heat station, comprising a fluidtight housing having a displacer movable therein to define a first fluid chamber of variable volume and a second fluid chamber of variable volume, means to move said displacer, and a fluid flow path providing fluid communication between said chambers, said flow path incorporating first and second heat storage means, said second heat storage means being located within said displacer, characterized in that said first heat storage means is located within a fixed regenerator housing extending from said heat station through a portion of that length of said fluidtight housing and coaxial therewith to define an annular cavity within said housing, that said displacer is formed to have an annular section movable within said annular cavity to define said first chamber in the form of an annulus and that said second chamber is defined within said annular section of said displacer.
 3. A cryogenic apparatus, comprising in combination a. a housing terminating at its cold end in means adapted to deliver refrigeration; b. a cylindrical tubing internal of and coaxial with said housing, extending from said cold end through a portion of the length of said housing and defining an annular spacing with the internal wall of said housing; c. a first regenerator within said cylindrical tubing; d. a displacer movable within said housing and comprising a cylindrical portion and an extended annular portion, said annular portion being adapted to move within said annular spacing; e. a second regenerator located within said cylindrical portion of said displacer; f. a first refrigeration chamber within said annular spacing Having a volume variable with the movement of said displacer and in fluid communication with said first regenerator; g. a second refrigeration chamber defined within said annular portion of said displacer, having a volume variable with the movement of said displacer and in fluid communication with said first and second regenerators; h. fluid flow path means including said regenerators and refrigeration chambers and adapted to permit fluid circulation through said apparatus; and i. means to impart motion to said displacer.
 4. An apparatus in accordance with claim 3 including a third chamber of variable volume, said third chamber being in fluid communication with said second regenerator.
 5. An apparatus in accordance with claim 4 wherein said third chamber is within said housing and said apparatus includes a piston operating in conjunction with said displacer to vary the volume of said third chamber.
 6. An apparatus in accordance with claim 3 including a second displacer having heat storage means therein and being independently operable to define third and fourth chambers of variable volume, said third and fourth chambers having heat transfer means associated therewith.
 7. An apparatus in accordance with claim 3 wherein said housing and said cylindrical portion of said displacer are of a stepped configuration, thus having two sections of different diameter and defining a third refrigeration chamber of variable volume, and wherein the larger-diameter section of said displacer contains a third regenerator in fluid communication with said third refrigeration chamber and said third regenerator is part of said fluid flow path means.
 8. An apparatus in accordance with claim 7 including a fourth chamber of variable volume, said fourth chamber being in fluid communication with said third regenerator.
 9. An apparatus in accordance with claim 3 wherein said cylindrical tubing and the internal configuration of said annular portion of said displacer are stepped, thereby defining a third refrigeration chamber of variable volume within said displacer, and wherein said tubing contains a third regenerator in fluid communication with said second and third refrigeration chambers and said first regenerator.
 10. An apparatus in accordance with claim 3 wherein said means to impart motion to said displacer comprises a rod and means to drive said rod whereby said displacer is driven mechanically.
 11. An apparatus in accordance with claim 3 wherein said means to impart motion to said displacer comprises a piston affixed to said displacer, a fluid chamber associated with said piston, and means to introduce into and withdraw a fluid from said fluid chamber whereby said displacer is driven pneumatically.
 12. An apparatus in accordance with claim 3 wherein that part of said annular portion of said displacer which defines said second refrigeration chamber is formed of a material exhibiting high heat conductivity whereby heat may be exchanged between the fluid in said second refrigeration chamber and an external load.
 13. An apparatus in accordance with claim 3 including high-pressure fluid supply means, a low-pressure fluid reservoir, and valve-controlled fluid conduit means providing fluid communication between said fluid supply means and said fluid reservoir and said second regenerator.
 14. An apparatus in accordance with claim 13 wherein said high-pressure fluid supply means and said low-pressure fluid reservoir are combined in the form of a fluid compressor.
 15. An apparatus in accordance with claim 13 including a third chamber of variable volume positioned in said fluid flow path between said valve-controlled fluid conduit means and said second regenerator.
 16. A cryogenic apparatus adapted to deliver refrigeration to an external load at a plurality of temperature levels, comprising in combination a. a housing formed in a stepped configuration and having two coaxial sections of different diameters, the end of the smaller-diameter section beinG the cold end and being adapted to deliver refrigeration at the lowest temperature; b. a cylindrical tubing internal of said smaller-diameter section, extending from said cold end through a portion of the length of said smaller-diameter section and defining an annular spacing with the internal wall thereof; c. a first regenerator within said cylindrical tubing; d. a displacer of stepped configuration formed of two sections of different diameters, the larger-diameter section being movable in the larger-diameter housing section and the smaller-diameter section being movable in the smaller-diameter housing section, the smaller-diameter section having a cylindrical portion and an extended annular portion, said annular portion being adapted to move within said annular spacing; e. a second regenerator located within said cylindrical portion of said smaller-diameter section of said displacer; f. a third regenerator located within said larger-diameter section of said displacer; g. a first refrigeration chamber within said annular spacing having a volume variable with the movement of said displacer and in fluid communication with said first regenerator; h. a second refrigeration chamber defined within said annular portion of said displacer, having a volume variable with the movement of said displacer and in fluid communication with said first and second regenerators; i. a third refrigeration chamber defined in said larger-diameter housing section, having a volume variable with the movement of said displacer and in fluid communication with said second and third regenerators; j. fluid flow path means including said regenerators and refrigeration chambers and adapted to permit fluid circulation through said apparatus; k. heat station means associated with at least said first refrigeration chamber and said third refrigeration chamber and adapted to effect heat exchange between fluid in said chambers and an external load; and l. means to impart motion to said displacer.
 17. An apparatus in accordance with claim 16 wherein heat station means are associated with said second refrigeration chamber and wherein that part of said annular portion of said displacer which defines said second refrigeration chamber is formed of a material exhibiting high heat conductivity whereby heat may be exchanged between the fluid in said second refrigeration chamber and said heat station means associated therewith.
 18. An apparatus in accordance with claim 16 wherein said external load comprises a Joule-Thomson loop.
 19. An apparatus in accordance with claim 16 including a fourth chamber of variable volume, said fourth chamber being in fluid communication with said third regenerator.
 20. An apparatus in accordance with claim 19 wherein said fourth chamber is within said housing and said apparatus includes a piston operating in conjunction with said displacer to vary the volume of said fourth chamber.
 21. An apparatus in accordance with claim 16 including a second displacer having heat storage means therein and being independently operable to define fourth and fifth chambers of variable volume, said fourth and fifth chambers having heat transfer means associated therewith.
 22. An apparatus in accordance with claim 16 including high-pressure fluid supply means, a low-pressure fluid reservoir, and valve-controlled fluid conduit means providing fluid communication between said fluid supply means and said fluid reservoir and said second regenerator.
 23. An apparatus in accordance with claim 22 wherein said high-pressure fluid supply means and said low-pressure fluid reservoir are combined in the form of a fluid compressor.
 24. An apparatus in accordance with claim 22 including a fourth chamber of variable volume positioned in said fluid flow path between said valve-controlled fluid conduit means and said second regenerator. 